Such a standby display device must make it possible to display, in the flight deck of the aircraft, minimum information [piloting information (speed, altitude, attitude) and navigation information] which is representative of the flight of the aircraft, in case of failure of a main display device of the aircraft, in particular a navigation screen of “ND” type (“Navigation Display”) or a primary piloting screen of “PFD” type (“Primary Flight Display”), or in case of failure of a system [ADIRS (“Air Data and Inertial Reference System”), FMS (“Flight Management System”), . . . ] formulating information customarily displayed on said main display devices of the aircraft (ND, PFD, . . . ).
There is known a first standby display device of the “ISIS” type (Integrated Standby Instrument System) which displays piloting information (altitude, speed and attitude) of the aircraft on a screen, whose man/machine interface resembles that of the PFD screen. Document FR-2 784 457 relates to such a first standby display device.
There is also known a second standby display device of the “DDRMI” type (“Digital Distance and Radio Magnetic Indicator”) which displays navigation information, such as the heading of the aircraft, as well as its position with respect to standard beacons, for example of “VOR” type (VHF Omnidirectional Range”) or of “DME” type (“Distance Measuring Equipment”).
These two standby display devices ISIS and DDRMI therefore display very different information.
However, neither of these devices ISIS and DDRMI is able, on its own, to display the aforesaid minimum piloting and navigation information. Moreover, even when an aircraft simultaneously comprises both these devices ISIS and DDRMI, there are still significant drawbacks in the standby display. Specifically, when the ISIS device has failed or is not available, the aircraft cannot take off for safety reasons, since the display of some information would not then be guaranteed in case of failure of the main display devices (PDF, ND, . . . ) during the flight. Furthermore, the DDRMI device does not cover the geographical zones where no VOR signal or DME signal exists (oceanographic zones, terrestrial zones poorly equipped with VOR or DME stations).
Moreover, document US 2002/0123830 discloses a particular primary piloting screen which, in addition to the information displayed customarily on a PFD screen (speed, altitude, attitude), also presents a heading scale on the horizon line, on which are displayed a first symbol representing the route followed by the aircraft and a second symbol representing the route to be followed so as to fly towards the next route point. This known screen cannot therefore be used as standby display device, since it does not display the minimum navigation information necessary, in particular it does not make it possible to ascertain the exact position of the next route point. Moreover, as the heading scale is situated directly on the horizon line, reading the information is rendered difficult.